Regarding fin-and-tube heat exchangers, tubes having circular cross sections and flat tubes of rounded rectangular shapes having high aspect ratios in cross section are known shapes of heat transfer tubes. In this specification, a heat exchanger using circular tubes will be referred to as a “circular tube heat exchanger” and a heat exchanger using flat tubes will be referred to as a “flat tube heat exchanger.”
To enhance the heat transmission performance of a heat exchanger, heat transfer tubes are arranged in a staggered pattern relative to fins (hereinafter referred to as a “staggered pattern”). In the circular tube heat exchanger, two rows of circular tubes are formed as one unit, and thus, the staggered pattern can be easily obtained. In the flat tube heat exchanger, however, flat tubes are inserted into fins, or slits of the fins are inserted into outer peripheral portions of flat tubes. To ease fabrication, the insertion is performed per row. Thus, in the flat tube heat exchanger, the staggered pattern is obtained by disposing a plurality of rows of heat exchangers in which flat tubes are disposed in units of rows, as described in, for example, Patent Literature 1.